How to draw a geospatial map using Ggplot2?

How to draw a geospatial map using Ggplot2?

Plotting geospatial data is a common visualisation task, and one that requires specialised tools. Typically the problem can be decomposed into two problems: using one data source to draw a map, and adding metadata from another information source to the map. This chapter will help you tackle both problems.

Where can I find the National Geodetic Survey datasheet?

The Datasheet can be retrieved by clicking on the PID in the list. What are the colored squares with numbers in them and what do the numbers mean? The squares are clusters of marks in that area.

Is the longitude data format used in real world mapping?

There are a few limitations to the approach outlined above, not least of which is the fact that the simple “longitude-latitude” data format is not typically used in real world mapping. Vector data for maps are typically encoded using the “simple features” standard produced by the Open Geospatial Consortium.

How do you make a map in cartopy?

This is done via the transform= keyword in the plotting method. The argument is another cartopy.crs object. If you don’t specify a transform, Cartopy assume that the data is using the same projection as the underlying GeoAxis. The core concept is that the projection of your axes is independent of the coordinate system your data is defined in.

How do you plot mi _ counties in ggplot2?

To get a better sense of what the data contains, we can plot mi_counties using geom_point (), as shown in the left panel below. In this plot, each row in the data frame is plotted as a single point, producing a scatterplot that shows the corners of every county.

What does Coord _ SF ( ) do in ggplot2?

The coord_sf () function governs the map projection, discussed in Section 6.3. In some instances you may want to overlay one map on top of another. The ggplot2 package supports this by allowing you to add multiple geom_sf () layers to a plot.

How do you adjust the axes in ggplot2?

In both plots I use coord_quickmap () to adjust the axes to ensure that longitude and latitude are rendered on the same scale. Chapter 16 discusses coordinate systems in ggplot2 in more general terms, but as we’ll see below, geospatial data often require a more exacting approach.

Why does ggplot2 give error for centroids?

The reason that it is giving you the error is because the inclusion of centroids.df needs to be a named variable (e.g. accompanied by “data=”) This issue was addressed here: How to deal with “data of class uneval” error from ggplot2?

Can you overlay one map on another in ggplot2?

In some instances you may want to overlay one map on top of another. The ggplot2 package supports this by allowing you to add multiple geom_sf () layers to a plot.

How to turn a scatterplot into a map?

To turn this scatterplot into a map, we use geom_polygon () instead, which draws each county as a distinct polygon. This is illustrated in the right panel below.

What kind of data is used in ggplot2?

For this reason, ggplot2 provides geom_sf () and coord_sf () to handle spatial data specified in simple features format. There are a few limitations to the approach outlined above, not least of which is the fact that the simple “longitude-latitude” data format is not typically used in real world mapping.